A psychologist contracted to help trauma victims at Travis Air Force Base in California left his patients "even more traumatized" by his own alleged sexual attacks, prosecutors say.

CBS Sacramento reported Monday that Dr. Heath Sommer was arrested earlier in May and entered not guilty pleas to multiple felony sexual assault and battery charges.

On Monday, prosecutors filed their official complaint against the clinical psychologist, detailing allegations that he used a technique known as exposure therapy on his patients -- inflicting the same sort of abuse on his patients that would have landed some of them in his office in the first place.

CBS Sacramento says the alleged abuse occurred between 2010 and 2016, and that Sommer faces charges including sexual battery, rape, and oral copulation. It was not clear how many alleged victims there were, or how many of them were already victims of sexual abuse before they sought treatment at the Air Force base.

In a statement released by Travis Air Force Base, spokesperson Traci Keller confirmed that the U.S. Air Force had contracted Sommer to work at the base's David Grant Medical Center, but said he was "no longer employed there."

"The United States Air Force and Travis Air Force Base have zero tolerance for sexual assault," Keller said in the statement.

According to CBS Sacramento, Sommer was detained on $750,000 bail at the Stanton Correctional Facility in Fairfield, just east of the base.

The base is located about 45 miles northeast of Sacramento and has been operating there for 75 years.